First, let’s make sure you have the Sentinel-1 Toolbox (S1TBX) installed. Check that you have a Radar menu on the top, check the about box for a S1TBX tab and go to Tools -> Plugins to see what version of S1TBX you have.
I do have a RADAR menu on the top, and also have the S1TBX modules installed. Check the document with attached images.
Are the files inside my .ZIP folder correct? people mention .xml files and I dont have any of those.
Then it should be able to open the S1A_.zip or S1B_.zip file or unzip, open the manifest.safe which is the xml file.
What is the product you are trying to open? What version os SNAP are you using? What error is given when you open the zip?